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ERC20 Token Solidity 0.4.23

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netkiller old

发布于 2018-05-17 08:30:10

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代码可运行

文章被收录于专栏：NetkillerNetkiller

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代码可运行

Netkiller Blockchain 手札

本文作者最近在找工作，有意向致电 13113668890

Mr. Neo Chan, 陈景峯(BG7NYT)

中国广东省深圳市龙华新区民治街道溪山美地 518131 +86 13113668890 <netkiller@msn.com>

文档始创于2018-02-10

转载请与作者联系，转载时请务必标明文章原始出处和作者信息及本声明。

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http://netkiller.github.io
http://netkiller.sourceforge.net

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QQ：13721218 请注明“读者”
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$Data$

内容摘要

这一部关于区块链开发及运维的电子书。

为什么会写区块链电子书？因为2018年是区块链年，区块链是一个风口，前几个风口我都错过了。例如web2.0, 云，大数据等等，都从身旁擦肩而过。所以我要抓住这次。

这本电子书是否会出版（纸质图书）？不会，因为互联网技术更迭太快，纸质书籍的内容无法实时更新，一本书动辄百元，很快就成为垃圾，你会发现目前市面的上区块链书籍至少是一年前写的，内容已经过时，很多例子无法正确运行。所以我不会出版，电子书的内容会追逐技术发展，及时跟进软件版本的升级，做到内容最新，至少是主流。

这本电子书与其他区块链书籍有什么不同？市面上大部分区块链书籍都是用2/3去讲区块链原理，只要不到 1/3 的干货，干货不够理论来凑，通篇将理论或是大谈特谈区块链行业，这些内容更多是头脑风暴，展望区块链，均无法落地实施。本书与那些书籍完全不同，不讲理论和原理，面向应用落地，注重例子，均是干货。

写作原则，无法落地的项目作者绝对不会写。凡是写入电子的内容均具备可操作，可落地。

电子书更新频率？每天都会有新内容加入，更新频率最迟不会超过一周，更新内容请关注 https://github.com/netkiller/netkiller.github.io/commits/master

本文采用碎片化写作，原文会不定期更新，请尽量阅读原文。

http://www.netkiller.cn/blockchain/index.html

您的打赏是我的写作动力：http://www.netkiller.cn/blockchain/donations.html

接受 ETH 打赏：0x3e827461Cc53ed7c75A29187CfF39629FCAE3661

5.2. ERC20 Token Solidity 0.4.23

5.2.1. 构造方法

原合约

pragma solidity ^0.4.21;

contract NetkillerToken {
  address public owner;
  string public name;
  string public symbol;
  uint public decimals;
  uint256 public totalSupply;

  event Transfer(address indexed from, address indexed to, uint256 value);

  /* This creates an array with all balances */
  mapping (address => uint256) public balanceOf;

  function NetkillerToken(uint256 initialSupply, string tokenName, string tokenSymbol, uint decimalUnits) public {
    owner = msg.sender;
    name = tokenName;
    symbol = tokenSymbol;
    decimals = decimalUnits;
    totalSupply = initialSupply * 10 ** uint256(decimals);
    balanceOf[msg.sender] = totalSupply;
  }

  /* Send coins */
  function transfer(address _to, uint256 _value) public {
    /* Check if the sender has balance and for overflows */
    require(balanceOf[msg.sender] >= _value && balanceOf[_to] + _value >= balanceOf[_to]);

    /* Add and subtract new balances */
    balanceOf[msg.sender] -= _value;
    balanceOf[_to] += _value;

    /* Notify anyone listening that this transfer took place */
    emit Transfer(msg.sender, _to, _value);
  }
}

新版合约

pragma solidity ^0.4.23;

contract NetkillerToken {
  address public owner;
  string public name;
  string public symbol;
  uint public decimals;
  uint256 public totalSupply;

  event Transfer(address indexed from, address indexed to, uint256 value);

  /* This creates an array with all balances */
  mapping (address => uint256) public balanceOf;

  constructor(uint256 initialSupply, string tokenName, string tokenSymbol, uint decimalUnits) public {
    owner = msg.sender;
    name = tokenName;
    symbol = tokenSymbol;
    decimals = decimalUnits;
    totalSupply = initialSupply * 10 ** uint256(decimals);
    balanceOf[msg.sender] = totalSupply;
  }

  /* Send coins */
  function transfer(address _to, uint256 _value) public {
    /* Check if the sender has balance and for overflows */
    require(balanceOf[msg.sender] >= _value && balanceOf[_to] + _value >= balanceOf[_to]);

    /* Add and subtract new balances */
    balanceOf[msg.sender] -= _value;
    balanceOf[_to] += _value;

    /* Notify anyone listening that this transfer took place */
    emit Transfer(msg.sender, _to, _value);
  }
}

5.2.2. 官方规定 Method 方法

所有的ERC20代币都是按照下面这些方法来定义的。下面我们讲解一下每个方法的作用。

5.2.2.1. name

function name() view public returns (string name)

返回string类型的ERC20代币的名字，例如：Netkiller Reader Coin

5.2.2.2. symbol

function symbol() view public returns (string symbol)

返回string类型的ERC20代币的符号，也就是代币的简称，例如：NRC。

5.2.2.3. decimals

function decimals() view public returns (uint decimals)

支持几位小数点后几位。如果设置为3。也就是支持0.001表示。

5.2.2.4. totalSupply

function totalSupply() view public returns (uint256 totalSupply)

发行代币的总量，可以通过这个函数来获取。所有智能合约发行的代币总量是一定的，totalSupply必须设置初始值。

5.2.2.5. balanceOf

function balanceOf(address _owner) public returns (uint256 balance)

输入地址，可以获取该地址代币的余额。

5.2.2.6. transfer

function transfer(address _to, uint256 _value) public returns (bool success)

调用transfer函数将自己的token转账给_to地址，_value为转账金额

5.2.2.7. approve

function approve(address _spender, uint256 _value) public returns (bool success)

批准_spender账户从自己的账户转移_value个token。可以分多次转移。

5.2.2.8. transferFrom

function transferFrom(address _from, address _to, uint256 _value) public returns (bool success)

与approve搭配使用，approve批准之后，调用transferFrom函数来转移token。

5.2.2.9. allowance

function allowance(address _owner, address _spender) public returns (uint256 remaining)

返回_spender还能提取token的个数。

approve、transferFrom及allowance解释：账户A有1000个代币，想允许B账户随意调用100个代币。A账户按照以下形式调用approve函数approve(B,100)。当B账户想用这100个代币中的10个代币给C账户时，则调用transferFrom(A, C, 10)。这时调用allowance(A, B)可以查看B账户还能够调用A账户多少个token。

5.2.3. 事件

5.2.3.1. Transfer

event Transfer(address indexed _from, address indexed _to, uint256 _value)

当成功转移token时，一定要触发Transfer事件

5.2.3.2. Approval

event Approval(address indexed _owner, address indexed _spender, uint256 _value)

当调用approval函数成功时，一定要触发Approval事件

完整的例子

https://etherscan.io/address/0x6333050c7a025027b51a8039cbafd2584933299d#code

pragma solidity ^0.4.21;

/******************************************/
/*       Netkiller ADVANCED TOKEN         */
/******************************************/
/* Author netkiller <netkiller@msn.com>   */
/* Home http://www.netkiller.cn           */
/* Version 2018-05-09 - Add Global lock   */
/******************************************/

contract NetkillerToken {
    address public owner;
    // Public variables of the token
    string public name;
    string public symbol;
    uint public decimals;
    // 18 decimals is the strongly suggested default, avoid changing it
    uint256 public totalSupply;

    // This creates an array with all balances
    mapping (address => uint256) public balanceOf;
    mapping (address => mapping (address => uint256)) public allowance;

    // This generates a public event on the blockchain that will notify clients
    event Transfer(address indexed from, address indexed to, uint256 value);

    // This notifies clients about the amount burnt
    event Burn(address indexed from, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);
    
    mapping (address => bool) public frozenAccount;

    /* This generates a public event on the blockchain that will notify clients */
    event FrozenFunds(address target, bool frozen);

    bool lock = false;

    /**
     * Constrctor function
     *
     * Initializes contract with initial supply tokens to the creator of the contract
     */
    function NetkillerToken(
        uint256 initialSupply,
        string tokenName,
        string tokenSymbol,
        uint decimalUnits
    ) public {
        owner = msg.sender;
        name = tokenName;                                   // Set the name for display purposes
        symbol = tokenSymbol; 
        decimals = decimalUnits;
        totalSupply = initialSupply * 10 ** uint256(decimals);  // Update total supply with the decimal amount
        balanceOf[msg.sender] = totalSupply;                // Give the creator all initial token
    }

    modifier onlyOwner {
        require(msg.sender == owner);
        _;
    }

    modifier isLock {
        require(!lock);
        _;
    }
    
    function setLock(bool _lock) onlyOwner public{
        lock = _lock;
    }

    function transferOwnership(address newOwner) onlyOwner public {
        if (newOwner != address(0)) {
            owner = newOwner;
        }
    }
 
    /* Internal transfer, only can be called by this contract */
    function _transfer(address _from, address _to, uint _value) isLock internal {
        require (_to != 0x0);                               // Prevent transfer to 0x0 address. Use burn() instead
        require (balanceOf[_from] >= _value);               // Check if the sender has enough
        require (balanceOf[_to] + _value > balanceOf[_to]); // Check for overflows
        require(!frozenAccount[_from]);                     // Check if sender is frozen
        require(!frozenAccount[_to]);                       // Check if recipient is frozen
        balanceOf[_from] -= _value;                         // Subtract from the sender
        balanceOf[_to] += _value;                           // Add the same to the recipient
        emit Transfer(_from, _to, _value);
    }

    /**
     * Transfer tokens
     *
     * Send `_value` tokens to `_to` from your account
     *
     * @param _to The address of the recipient
     * @param _value the amount to send
     */
    function transfer(address _to, uint256 _value) public {
        _transfer(msg.sender, _to, _value);
    }

    /**
     * Transfer tokens from other address
     *
     * Send `_value` tokens to `_to` in behalf of `_from`
     *
     * @param _from The address of the sender
     * @param _to The address of the recipient
     * @param _value the amount to send
     */
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
        require(_value <= allowance[_from][msg.sender]);     // Check allowance
        allowance[_from][msg.sender] -= _value;
        _transfer(_from, _to, _value);
        return true;
    }

    /**
     * Set allowance for other address
     *
     * Allows `_spender` to spend no more than `_value` tokens in your behalf
     *
     * @param _spender The address authorized to spend
     * @param _value the max amount they can spend
     */
    function approve(address _spender, uint256 _value) public returns (bool success) {
        allowance[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }

    /**
     * Destroy tokens
     *
     * Remove `_value` tokens from the system irreversibly
     *
     * @param _value the amount of money to burn
     */
    function burn(uint256 _value) onlyOwner public returns (bool success) {
        require(balanceOf[msg.sender] >= _value);   // Check if the sender has enough
        balanceOf[msg.sender] -= _value;            // Subtract from the sender
        totalSupply -= _value;                      // Updates totalSupply
        emit Burn(msg.sender, _value);
        return true;
    }

    /**
     * Destroy tokens from other account
     *
     * Remove `_value` tokens from the system irreversibly on behalf of `_from`.
     *
     * @param _from the address of the sender
     * @param _value the amount of money to burn
     */
    function burnFrom(address _from, uint256 _value) onlyOwner public returns (bool success) {
        require(balanceOf[_from] >= _value);                // Check if the targeted balance is enough
        require(_value <= allowance[_from][msg.sender]);    // Check allowance
        balanceOf[_from] -= _value;                         // Subtract from the targeted balance
        allowance[_from][msg.sender] -= _value;             // Subtract from the sender's allowance
        totalSupply -= _value;                              // Update totalSupply
        emit Burn(_from, _value);
        return true;
    }

    /// @notice Create `mintedAmount` tokens and send it to `target`
    /// @param target Address to receive the tokens
    /// @param mintedAmount the amount of tokens it will receive
    function mintToken(address target, uint256 mintedAmount) onlyOwner public {
        uint256 _amount = mintedAmount * 10 ** uint256(decimals);
        balanceOf[target] += _amount;
        totalSupply += _amount;
        emit Transfer(this, target, _amount);
    }

    /// @notice `freeze? Prevent | Allow` `target` from sending & receiving tokens
    /// @param target Address to be frozen
    /// @param freeze either to freeze it or not
    function freezeAccount(address target, bool freeze) onlyOwner public {
        frozenAccount[target] = freeze;
        emit FrozenFunds(target, freeze);
    }
}